Liquid crystal displays (LCDs) are very popular at the present time and are utilized in a great variety of direct view type displays and virtual image displays. Examples of direct view displays in which LCDs are utilized include digital watches, telephones, lap-top computers and the like. Examples of virtual image displays in which LCDs are utilized include camcorder viewfinders, head-mounted displays, or virtual displays in portable electronic equipment, such as portable communications equipment. In general, during operation liquid crystal devices are illuminated with a relatively large, separately mounted light source, preferably from the rear (back-lighting), so that most of the light travels directly through the liquid crystal and outwardly to the eye or eyes of a viewer. In some cases the LCD is front-lit with the light approaching the LCD from the front and reflecting back towards the viewers eye or eyes. Both direct view displays and virtual image displays require a substantial amount of light for suitable viewing. To provide a suitable amount of light or luminance at the outlet, the LCD requires a relatively bright, and large, backlight source. Generally, the result is to produce a relatively large and cumbersome package, usually with several discrete components that is not amenable to incorporation in portable electronic equipment, or the like.
Typically, red, green and blue light emitting devices (LEDs) have been very important to the development of a small LCD backlight. In the past, fluorescent lamps were used to light these small LCDs. Fluorescent lamps work very well at lighting large direct view LCDs, but are a problem at the smaller sizes including virtual image displays. As a general rule, as the length and diameter of the lamps decrease, the efficiency also decreases, making small lamps very power hungry. In addition, the individual red, green and blue emission from the fluorescent lamps cannot be controlled individually, thus field sequential color is difficult.
These problems severely limit the usefulness of liquid crystal displays. For example, in portable electronic devices such as telephones, two-way radios, pagers, etc. the displays are limited to a few alpha-numeric digits viewed as a direct view image. Generally, if a small portable device is desired, the display must be reduced to a very small number of digits, since the size of the display dictates the minimum size of the device into which it is integrated.
One way to alleviate these problems is to use an illumination device in combination with a spatial light modulator (SLM), to act as the image source with a magnifying optical system. This can take the form of a projection display, in which the light modulated by the liquid crystal or SLM is projected by the optical system onto a diffusing screen, or it can take the form of a virtual image display, where the optical system creates a large virtual image of the small image created by the illumination device and SLM combination. In this application the SLM used is an LCD, but it should be understood that other forms of SLMs, such as micromachined silicon, diffractive devices, deformable mirrors, or the like are possible.
When using this configuration as a virtual image display, the number of discrete components still results in a large and cumbersome package. At present, it is extremely difficult to provide a sufficiently large illumination device while maintaining minimal size so that the LCD is properly illuminated, can be viewed conveniently, and is capable of field sequential color to achieve a full color image.
Thus, it would be beneficial to provide for a full color backlight that allows for incorporation into portable electronic devices that utilize liquid crystal displays.
It is a purpose of the present invention to provide for a new and improved illumination device that serves as a backlight for a transmissive liquid crystal display.
It is another purpose of the present invention to provide for a new and improved organic light emitting device (OLED) backlight for use as a LCD illumination device in a liquid crystal display.
It is another purpose of the present invention to provide for a new and improved OLED backlight for use as a LCD illumination device that is hermetically sealed to provide for a more reliable light source.
It is a further purpose of the present invention to provide a new and improved OLED backlight for use as a LCD illumination device which is small and compact enough to be utilized in portable electronic equipment.
It is a still further purpose of the present invention to provide a new and improved OLED backlight for use as a LCD illumination device which requires a sufficiently small amount of power to be utilized in portable electronic equipment.
It is yet another purpose of the present invention to provide a new and improved OLED backlight for use as a LCD illumination device that allows for field sequential color.
It is another purpose of the present invention to provide for a new and improved OLED backlight that has integrated as a part thereof a liquid crystal display.